1. Field of the Invention
The present invention relates generally to an actual road simulated endless belt arrangement for a bench testing apparatus. More specifically, the invention relates to a hydrodynamic supporting structure for the belt arrangement with improved drain structure.
2. Description of the Background Art
Endless belt type bench testing apparatus for testing vehicular tires, vehicular performance have been developed. Utilizing such endless type bench testing apparatus, a simulated road test equivalent to the test to be performed on an actual road can be performed. For example, in case of tire test, deformation of tire or tire tread and/or slip angle at variety of tire load, camber angle and so forth. On the other hand, in case of the vehicular bench test on a chassis dynamometer, fuel economy test, engine performance test, endurance test and so forth can be performed by mounting all of the road wheels of the vehicle on the endless belt. Such bench testing apparatus employs a hydrodynamic supporting structure for an endless belt for providing support and bearing at a portion where load is applied. The hydrodynamic support has been proposed in the U.S. Pat. No. 4,324,128, issued on Apr. 13, 1982. The bench testing apparatus includes a pair of rotary drums and the endless belt formed of a flexible metallic belt. An intermediate portion between the rotary drums serves for supporting tire treads for testing performance of the tire per se and/or the vehicle, which intermediate portion will be hereafter referred to as "road simulated portion". A hydrodynamic support structure is provided for the road simulated portion for supporting the flexible metallic belt against load, i.e. load on the tire. In order to establish the hydrodynamic support and bearing for the flexible metallic belt, fluid medium, such as water, lubricant or so forth, is supplied beneath the flexible metallic belt for forming a thin and high pressure fluid layer.
Japanese Patent First (unexamined) Publication (Tokkai) Showa 56-129836 discloses the endless belt type bench testing apparatus which utilizes a dynamic pressure of the supporting fluid medium. In the disclosed structure, a supporting base is provided beneath the flexible metallic belt in a spaced apart relationship with maintaining a clearance therebetween. Water as the supporting fluid medium is supplied into the clearance between the support base and the flexible metallic belt for hydrodynamically establishing a pressurized fluid layer for supporting the load to be exerted on the road simulated portion. In such construction, the hydrodynamically generated pressure in the fluid layer serves for supporting the flexible metallic belt. On the other hand, Japanese Patent First Publication (Tokkai) Showa 55-128140 discloses another type of the endless belt type bench testing apparatus which utilizes a hydrostatic pressure of the supporting fluid medium.
In either of the aforementioned apparatus, the endless belt is driven at substantially high speed. As a result of high speed motion of the belt, the water forming the hydraulic bearing layer between the belt and support tends to be fed toward the downstream end in the motion direction of the endless belt. Therefore, large amount of water is discharged in the drainage groove at the portion corresponding to the downstream end of the belt path. As can be appreciated, since the large amount of water is drained at the downstream end of the belt path, water absorption capacity of the felt seal can be easily saturated within a short period to cause oozing of water out of the water drain circuit to encounter the aforementioned rusting problem for the components of the apparatus.
Furthermore, in the prior proposed technologies as set forth above, a seal member is provided in the vicinity of the drain path for assuring collection of the water discharged from the clearance between the belt and the support and for assuring avoidance of overflowing of the water from the drainage circuit. In the prior proposed apparatus, the seal member comprises a felt or the like provided in liquid-tight contact with the belt surface. For assuring liquid-tight seal, the felt seal is biased toward the belt surface for establishing resilient and tight contact thereto. This clearly results in increasing of magnitude of wearing of the seal member for causing degradation of the sealing ability in relatively short period. Since once water leakage is caused over the felt seal, rusting of metallic components may be caused. Therefore, in order to prevent the water from leaking, short interval maintenance has been required for causing increasing of the cost for operation.